Flap closure for containers

ABSTRACT

An elongated, flexible strap having an enlarged, T-shaped locking head at one end and an attached locking tongue on the opposite end is utilized to hold foldable closure flaps of a fiberboard container in a closed position by engaging the locking head in a slot in a closure flap, extending the strap over one edge of the container and engaging the locking tongue in a slot in an adjacent container wall. The locking tongue is offset from the strap and extends towards the locking head from its connection to the strap body.

United States Patent Pfaffendorf et a1.

.1151 3,707,023 1451 Dec. 26,1972

[54] FLAP CLOSURE FOR CONTAINERS [72] Inventors: James L. Pfaifendorf, Maple Grove; Marlyn D. Johnson, Minneapolis, both of Minn.

[73] Assignee: Saico Products Co., Minneapolis,

' Minn.

[22] Filed: May 14, 1971 [211 Appl. No.: 143,540

[52] US. Cl. ..24l8 5 B, 229/45, 292/253 [51] Int. Cl. ..A44b 9/00, 865d 45/00, E65c 19/18 [58] Field of Search ...24/73 PF, 85 B, 81 BF, 201 A,

[56] References Cited UNITED STATES PATENTS 392,224 11/1888 Reece ..229/47 UX 805,389 11/1905 Swanson ..24/201 A UX 915,045 3/1909 Schleicher ..292/253 2,611,530 9/1952 George ..24/81 BF UX 2,619,276 11/1952 Gibbons.....' ..229/45 UX 12/1910 Barsness Primary Examiner-Donald A. Griffin Attorney-Williamson, Palmatier & Bains, 11. Dale Palmatier, Herman H. Bains and Malcolm L. Moore [57] 1 ABSTRACT An elongated, flexible strap having an enlarged, T- shaped locking head at one end and an attached locking tongue on the opposite end is utilized to hold foldable closure flaps of a fiberboard container in a closed position by engaging the locking head in a slot in a closure flap, extending the strap over one edge of .the container and engaging the locking tongue in a slot in an adjacent container wall. The locking tongue is offset from thestrap and extends towards the locking head from its connection to the strap body.

14 Claims, 7 Drawing Figures FLAP CLOSURE FOR CONTAINERS BRIEF SUMMARY OF THE INVENTION This invention is directed to a container closure device specifically developed to provide a quick, easy and inexpensive means of positively locking closure flaps of a container in a closed position and of releasing and opening the closure flaps to obtain access to the container. String ties traditionally used to hold foldable closure flaps of fiberboard containers in a closed position by being wrapped around a lock button suffer from the disadvantages of being easily broken, disengaged and lost and of being difficult to secure in such a way that they maintain container flaps closed in a tight, secure position after attachment without becoming slack.

These disadvantages of string ties are overcome, and the foregoing basic objective is achieved, by a closure device particularly characterized by an elongated, flexible strap having an enlarged, locking head at-one end thereof and a locking tongue adjacent the opposite end portion thereof, the tongue being formed from a length of the strap material and attached thereto along a transverse line from which the tongue extends longitudinally of the strap towards the enlarged locking head and terrninates at a free end. The strap is easily and quickly engaged to hold a foldable closure flap in a tight, closed position by simply engaging the enlarged locking head within a slot in a closure flap, bending the strap over an adjacent edge of the container in overlaying relation to a container wall disposed at right angles to the closure flap in its closed position, and inserting the locking tongue in a slot provided in the container wall. The closure .strap is readily disengaged from the container wall slot by pulling on the tongue end of the strap in such a direction away from the slot as to flex the strap and thereby angle the locking tongue away from the aforesaid container wall so that it can be pulled out of the slot.

The tongue of the closure strap is rendered particularly effective as a locking device by forming the tongue from a length of the strap material to a configuration in which the tongue is permanently offset from the body of the strap and is attached thereto by an interconnecting shoulder portion angularly disposed with respect to the strap, with the shoulder portion thereby serving to hold the tongue at a spaced apart location with respect to the strap body. This tongue configuration permits the tongue to extend within a receiving slot of a container wall in a position wherein it is substantially parallel to the container wall in overlying relation thereto with the aforesaid shoulder portion of the tongue extending through the wall slot directly under the top edge of the slot. In such a locking position, the tongue of the closure strap will not be displaced and disengaged from the wall slot by rough handling or dropping of the container to which it is attached.

A further advantageous feature of the closure strap resides in the provision of at least one elongated, raised rib on the strap extending lengthwise on the end portion thereof from which said locking tongue is formed with the rib extending both forwardly and rearwardly of the line along which the tongue is attached to the strap. Such a rib serves to rigidify the strap along the length thereof over which the rib extends, thereby tending to prevent flexing of the strap along its juncture line with the strap and the resultant displacement of the tongue when it is engaged in a slot in a container wall.

The secure, locking engagement of the aforesaid strap tongue within a slot of a container wall is further enhanced by striking a tab from a container wall to form the aforesaid slot and folding the tab inwardly along a hinge line, with the tab being foldedto a position wherein it is in overlying relation to the inner surface of the container wall; and providing a raised detent on the free end of the locking tongue with the detent being restrainably engaged with the inner edge of the slot tab to assist in holding the tongue in place.

These and other objects and advantages of our inven tion will be readily understood by reference to the accompanying drawings wherein like reference numerals have been used to designate like elements throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 5 is a vertical section view taken along lines 5- 5 of FIG. 4 and showing the engagement of the lock strap with the container on an enlarged scale;

FIG. 6 is a fragmentary, vertical section view taken along lines 6-6 of FIG. 5; and

FIG. 7 is a fragmentary, top, plan view of the fiberboard container of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 through 3 of the drawings illustrate a preferred form of the closure device of. this invention,

wherein the device takes the form of an elongated strap generally designated by reference numeral 1. Strap 1 is made from material which is sufficiently flexible to permit the strap to be bent and flexed during application, but which has sufficient strength that the strap will be substantially self supporting in the configuration shown. Although various materials may be used for this purpose, we have found that strap 1 can be satisfactorily molded as a plastic piece and that polypropylene is particularly suitable for this purpose.

Strap 1 includes a relatively narrow, intermediate length 2 which has an enlarged locking head 4 formed on one end thereof. Head 4 preferably takes the form of a cross member 5 extending transversely with respect to narrow strap length 2 and of a greater width than strap length 2 so as to define therewith a substantially T-shaped locking head 4. Head 4 is reinforced by a pair of ribs 6 and 8 integrally formed thereon with rib 6 extending lengthwise of cross member 5 and rib 8 extending at right angles thereto for a short distance lengthwise of narrow strap portion 2. Rib 8 cooperates with an additional pair of ribs in a manner hereinafter described to limit and control the flexing of strap 1.

Narrow strap length 2 joins locking head 4 with an enlarged gripping head 10 formed on the opposite end portion of strap 1 to include a locking tongue 12.

the order of one and one-half inches, to serve as a 106012 oolo gripping surface which may readily be grasped between the thumb and forefinger for application of strap 1 to a container. Locking tongue 12 extends substantially longitudinally of strap 1 and comprises a length of strap material displaced from head portion and having a free end 14. Tongue 12 is attached to strap 1 along a juncture line 16 extending transversely of the strap with tongue 12 extending from line 16 towards locking head 4 and terminating a free end 14. Interconnecting strap 1 and tongue 12 at line 16 is a shoulder portion 18 of tongue 12 which is angularly disposed with respect to strap 1 and serves to hold tongue 12 at a permanently offset position from strap 1 at a spaced apart location with respect thereto as is clearly indicated in FIG. 2. A reinforcing rib 20 formed integrally with tongue 12 and extending lengthwise thereon is securely joined to strap head portion 10 at its base end 200 and strengthens and reinforces tongue 12. With head 10 under stress, rib 20 holds tongue 12 in the offset position from strap 1 illustrated in FIGS. 1 and 2. At its forward or free end 14, tongue 12 is formed to provide a raised detent 22 on the side of tongue 12 facing towards strap 1' in the manner shown in FIGS. 1 and 2. Detent 22 assists in holding tongue 12 in locking engagement with a slot of a container in a manner hereinafter explained.

Oriented Iongitudinallyalong gripping head 10 of strap 1 are a pair of ribs 24 and 25 which are disposed at laterally spaced locations on opposite sides of tongue juncture line 16. Ribs 24 and 25 are formed integrally with strap 1 and extend lengthwise thereof both forwardly and rearwardly of line 16. Ribs 24 and 25 not only lend strength to strap 1, but, more importantly they serve to prevent the flexing or bending of strap 1 about line 16. Because they extend both forwardly and rearwardly of line 16, ribs 24 and 25 substantially lessen the tendency of strap 1 to bend or pivot line 16, thereby preventing the angular displacement of tongue 12 with respect to the body of strap 1 along line 16 and the resultant disengagement of tongue 12 from a locking position within a slot on a container wall. Also, ribs 24 and 25 cooperate with rib 8 to define a length of strap 1 therebetween within which strap 1 is free to flex and bend as it is applied to a container. The resultant restricted flexing of strap 1 facilitates its attachment to a container in the manner explained below with reference to FIGS. 4 through 7.

As noted above, closure strap 1 is preferably molded as an integral unit from plastic material, polypropylene being the preferred plastic. Utilizing an injection molding process, tongue 12 is formed as an integral piece of strap 1 with the contour and permanently offset position from the body of strap 1 illustrated in FIGS. 1 and 2. Ribs 6, 8, 24 and 25 are also molded as integral components of strap 1. It is possible that the closure strap could be stamped or die cut out of strips of plastic material with tongue 12 being struck or cut from end portion 10 and permanently formed to the offset position shown in FIGS. 1 and 2 by forming angularly disposed shoulder 18 thereon.

In FIGS. 4 through 7 we have illustrated one, preferred manner of utilizing closure strap 1 to secure foldable flaps of a fiberboard container in a closed position. In FIG. 4 there is shown a fiberboard container 26 of the transfer file type having a pair of opposed closure flaps 28 and 29 hingedly attached to parallel edges 30 and 31 of the container and foldable inwardly towards each other to a closing position in overlying relation to the open, top end of the container. In FIG. 4, closure flaps 28 and 29 are shown in their inwardly folded, closed positions with two of the closure straps 1 being utilized at opposite ends of container 26 to hold flaps 28 and 29 closed. The preferred manner of attachment of straps 1 to the container and its closure flaps may be understood most .clearly by reference to FIGS. 4, 5 and 6. A first slot or aperture 32 is formed in at least one of the closure panels 28 or 29 at a location thereon adjacent one end of the closure flap in proximity to the inner, free edge thereof. Such a first slot 32 is shown in closure panel 28 in proximity toits inner, free edge 280 which must be held down to maintain flap 28 in its inwardly folded, closed position. Slot 32is located adjacent to one end of flap 28 near end wall 34 of container 26. A second slot 36 is formed in container wall 34 adjacent an upper edge 38 thereof which is one of the edges cooperating to define the open, top end of container 1. Wall 34 extends substantially at right angles to the plane in which closure flaps 28 and 29 are disposed in their box closing position shown in FIG. 4.

Flaps 28 and 29 overlap at their inner edges, and closure strap 1 is utilized to hold them closed by engaging locking head 4 of strap 1 within slot 32 of upper flap 28 and then pulling strap 1 over container edge 38 and bending or flexing it downwardly and engaging locking tongue 12 within wall slot 36. Aperture 32 in closure flap 28 is preferably an elongated, relatively narrow slot extending in a direction parallel to flap inner edge 28a; and, locking head 4 of strap 1 is initially inserted within slot 32 by holding strap 1 in a direction substantially perpendicular to slot 32 so that enlarged cross member 5 can be more easily inserted through slot 32. Then, strap 1 is pivoted to the position shown in FIGS. 5 and 6 so that cross member 5 will extend transversely of slot 32 and bear against the underside of panel 28 in restraining engagement therewith. As may be noted most clearly by reference to FIG. 5, the location of ribs 8, and 24, 25 controls and induces the bending of strap 1 in such a way that it may readily be flexed around edge 38 of box 26 and end wall 34 in overlying relation thereto to position tongue 12 for insertion within slot 36. As is indicated in FIG. 5, enlarged gripping end 10 of strap 1 may be flexed outwardly slightly at location 1a thereon at the forward end of ribs 24 and 25 in order to position tongue 12 in such a way that it may more easily be thrust forwardly and upwardly into slot 36. In its locking position of restraining engagement with slot 36 of container wall 34, tongue 12 will extend substantiallyv parallel to wall 34 with shoulder 18 thereof bearing against the upper edge of slot 36 in the manner shown in FIG. 5. By reason of the offset position of tongue 12 with respect to strap 1, utilizing angled shoulder portion 18, tongue 12 will be hooked over container wall 34 with shoulder portion 18 extending through wall slot 36 a sufficient distance to permit tongue 12 to extend upwardly along wall 34. The substantially parallel orientation of tongue 12 with respect to the body of strap 1 permits the firm gripping of container wall 34 therebetween.

The tight engagement of closure strap 1 with container wall 34 is further enhanced by striking or cutting tab 40 from container wall 34 to form slot 36, tab 40 being folded inwardly along a hinge line 41 where it is attached to container wall 34. Lock tongue 12 extends over slot tab 40 and holds it in an inwardly folded position wherein it is in overlying relation to the inner surface of container wall 34. Tab 40 and tongue 12 are of predetermined length such that tongue 12 will extend beyond the free end of tab 40 with detent 22 restrainably engaged with the inner edge 40a of tab 40 in the manner shown in FIG. 5. The engagement of tongue detent 22 with tab 40 further assists in holding locking tongue 12 in secure engagement with container wall 34. It is to be noted that the disposition of ribs 24 and 25 on strap 1, with these ribs extending both forwardly and rearwardly of the juncture line connection 16 of tongue 12 with strap end portion 10, tends to prevent the flexing of strap 1 along line 16, thereby preventing the pivotal movement of tongue 12 downwardly and outwardly away from wall 34, and the resulting loosening of disengagement of tongue 12 from the container wall.

With locking tongue 12 firmly engaged with container wall 34 through slot 36, and with T-shaped locking head 4 in restraining engagement with top closure flap 28 through slot 32 therein, flap 28 will be securely held in its inwardly folded closure position shown in FIG. 4. With the inner edge 28a of flap 28 overlapping the inner end 29a of opposed closure flap 29, as is clearly indicated in FIG. 6, flap 28 will hold flap 29 down in its closed position. Enlarged closure head 4 will be disposed between the inner ends of flaps 28 and 29 and will bear against the top surface of lower flap 29 in the arrangement shown in FIGS. 5 and 6. Utilizing two of the closure straps 1 at opposite ends of closure flap 28 in the arrangement shown in FIG. 4, flaps 28 and 29 will be held tightly closed in covering relation to the top of container 26.

Closure strap 1 can be quickly and easily disengaged from container wall 34 in order to open flaps 28 and 29 by simply gripping head of strap 1 and pulling upwardly and outwardly thereon so as to flex strap 1 at point la indicated in FIG. 5. This will have the effect of flexing end 10 of strap 1 outwardly and upwardly about point In with the result that tongue 12 will be pivoted downwardly, as viewed in the arrangement of FIG. 5, to a position wherein upward, lifting movement on gripping head 10 of strap 1 will permit tongue 12 to be pulled completely out of wall slot 36. Closure flaps 28 and 29 can then be folded outwardly to their open positions about their hinge line connections with upper edges 30 and 31 of box 26. Straps 1 will normally be left attached to closure panel 28 by the engagement of locking heads 4 through slots 32 therein so that the closure straps 1 will not be lost or misplaced until such time as the containeris again closed. It is to be noted that container 26 has a second set of end closure flaps 42 hingedly attached to the upper edge of end wall 34, and the opposite end wall (not shown) and utilized in a conventional manner to cooperate with elongated flaps 28 and 29 to fully and tightly close the top of container 1. These additional end flaps are folded inwardly first in the usual manner before flaps 28 and 29 are folded inwardly thereover. One of the end flaps 42 hingedly at- 6 tached to the upper edge 38 of end wall 34 is shown in FIGS. 5, 6 and 7.

In order to provide some means of adjusting the tightness of closure straps 1 on a container, both of the closure flaps 28 and 29 are provided with a receiving slot for locking head 4 of closure strap 1, one of the receiving slots being located closer to the container wall with which locking tongue 12 is engaged. This double slot feature for the closure flaps is illustrated in FIG. 7. It is to be noted that closure flap 29 is provided with a receiving slot 44 which is located adjacent the same end thereof as is slot 32 in flap 28 in proximity to inner edge 29a of flap 29. Slot 44 in closure flap 29 is located substantially closer to top edge 38 of container end wall 34 than is slot 32 in flap 28. Thus, flap 29 can be folded down last on top of flap 28 so as to utilize receiving slot 44 for the engagement of locking head 4 of closure strap 1. Because Slot 44 is located closer to container edge edge 38 and end wall 34 within which slot 36 is located, there will be a certain amount of slack in strap 1 and a looser fit of the closure strap on container 26 when locking tongue 12 is engaged within slot 36 of wall 34. This looser adjustment of closure strap 1 on the container will permit the expansion of the walls of container 26 when it is in a fully loaded condition.

It will be appreciated that closure strap 1 can be utilized to hold various types and arrangements of hinged closure flaps of containers in a closed position, utilizing a slot in one of the container walls to receive locking tongue 12. The double closure flap arrangement utilizing flaps 28 and 29 on a container 26 has been shown and described herein as one example of the manner in which closure strap 1 may be utilized on a container. Some containers may have only a single closure flap extending across an open end thereof with which locking head 4 of closure strap 1 would be engaged. It is possible that closure strap 1 could be utilized to hold two overlapping closure flaps together with strap I extending across the overlapping edges of the closure flaps in the same plane as the flaps in their closed positions. In such an application, locking head 4 would be engaged within a slot in one of the closure flaps, and tongue 12 would be engaged within an opposed slot in the other closure flap. The closing arrangement illustrated in FIGS. 4 through 6 wherein locking tongue 12 engages a slot in a container wall extending at right angles to the closure plane of the closure flaps is considered preferable as a way of positively holding the closure flaps closed in the event that the container should be turned upside down.

We contemplate that various changes and modifications can be made in the size, shape and configuration of closure strap 1, and in its manner of application to a container without departing from the spirit and scope of our invention as defined by the following claims.

We claim: I

1. A closure device for holding a hinged flap of a container in a closed position comprising:

a flexible, elongated strap having an enlarged locking head on one end thereof of greater width than said strap and extending transversely with respect thereto for insertion through a receiving aperture in a container closure flap; and

a locking tongue on the opposite end portion of said strap for insertion in a receiving slot in a container, said tongue extending substantially longitudinally of said strap and comprising a length of material displaced from said strap and having a free end directed towards said enlarged locking head, and said locking tongue being attached to said strap gaged within said first slot and extending therefrom over said one edge of said box wall in overlying relation to said wall, said strap having a locking tongue adjacent theopposite end portion along a juncture line extending substantially transthereof which is restrainably engaged in said versely of said strap at a location between said free second slot, said tongue comprising a length of end of said tongue and the outer edge of said opmaterial integral with said strap and attached posite end portion of said strap. thereto along a juncture line extending transverse- 2. A closure device as defined in claim 1 wherein: 1O ly of said strap, and said tongue extending from said locking tongue is attached to said strap at said juncture line by an interconnecting shoulder portion angularly disposed with respect to said strap,

said juncture line towards said enlarged locking head and terminating at a free end inserted within said second slot.

9. A fiberboard box and closure means as defined in claim 8 wherein:

there being a third slot is located at the other one of said shoulder portion serving to hold said tongue at a permanently offset position from said strap at a 1 spaced apart location with respect thereto.

3. A closure device as defined in claim 2, and further including: 1

a raised rib extending lengthwise on said tongue and said closure flaps adjacent the same end thereof as said first slot and in proximity to the inner free edge thereof, said third slot being closer to said one wall of said box than said first slot, and said having a base end securely joined to said opposite end portion of said strap, said rib serving to inner edges of said closure flaps being disposed in strengthen said tongue and to assist in holding said overlapping relation to each other when said flaps tongue in said offset position. are folded to said box closing position, whereby 4. A closure device as defined in claim 1, and further one or the other of said closure flaps may be folded including: on top of the other and said third slot selectively at least one elongated, raised rib on said strap exutilized to receive said enlarged locking head of tending lengthwise on said opposite end portion said closure strap to permit a looser fit of said clothereof both forwardly and rearwardly of said sure strap on said box, and thereby to accomjuncture line and thereby serving to prevent flexmodate the expansion of the walls of said box ing of said strap along said juncture line and the when it sin afully loaded condition.

10. A fiberboard box and closure means as defined in claim 8 wherein:

said second slot in said wall of said box is formed by striking a tab from said box wall and folding said tab inwardly along a hinge line where said tab joins said wall, said tab being folded inwardly to a position wherein it is in overlying relation to the inner surface of said box wall; and

a raised .detent on said free end of said locking tongue on the side thereof facing towards said elongated strap, said detent being restrainably engaged with the inner edge of said tab when said locking tongue is engaged within said second slot.

4 5 11. A fiberboard box and closure means as defined in claim 8 wherein:

said locking tongue is attached to said strap at said juncture line by an interconnecting shoulder portion angularly disposed with respect to said strap, said shoulder serving to hold said tongue at a perresultant displacement of said tongue when it is engaged in a slot in a container.

5. A closure device as defined in claim 1, and further including:

a pair of elongated, raised ribs on said strap extending lengthwise on said opposite end portion of said strap both forwardly and rearwardly of said juncture line at laterally spaced locations on opposite sides of said juncture line. 40

6. A closure device as defined in claiml wherein:

a raised detent is formed onsaid free end of said tongue on theside thereof facing towards said elongated strap.

7. A closure device as defined in claim 1 wherein:

said enlarged locking head extends transversely of said strap on both sides thereof and defines therewith a substantially T-shaped end on said strap.

8. On a fiberboard box having a pair of opposed closure flaps hingedly attached to parallel edges of the box and foldable inwardly towards each other to a box closing position, improved closure means releasably holding said closure flaps in said box closing position comprising: I

there being a first slot in one of said closure flaps adjacent one end thereof and in proximity to the inner, free edge thereof; juncture line and thereby serving to prevent flexthere being a second slot in one wall of said box ading of said strap along said juncture line and the jacent one edge thereof which is one of the edges resultant displacement of said tongue from encooperating to define an open end of said box gagement with said second slot in said box wall. closed by said closure flaps, and said one wall of 13. A fiberboard box and closure means as defined in said box extending at substantially right angles to claim 8wherein: the plane in which said flaps are disposed in said said enlarged locking head on said closure strap is of box closing position; and greater width than said strap and extends transvera flexible, elongated closure strap having an enlarged sely thereof, whereby said locking head defines locking head at one end thereof restrainably enwith said strap a substantially T-shaped end on said spaced apart location with respect thereto. 12. A fiberboard box and closure means as defined in claim 8, and further including:

at least one elongated, raised rib on said strap extending lengthwise on said opposite end portion thereof both forwardly and rearwardly of said manently offset position from said strap at a strap, said T-shaped end being oriented transversely of said first slot.

14. A closure device for holding a hinged flap of a container in a closed position comprising:

a flexible, elongated strap having an enlarged locking head at one end thereof for insertion through a receiving aperture in a container closure flap; and

a locking tongue adjacent the opposite end portion of said strap for insertion in a receiving slot in a container, said tongue comprising a length of 10 material displaced from said strap and attached thereto along a juncture line extending transverse- It i i i 

1. A closure device for holding a hinged flap of a container in a closed position comprising: a flexible, elongated strap having an enlarged locking head on one end thereof of greater width than said strap and extending transversely with respect thereto for insertion through a receiving aperture in a container closure flap; and a locking tongue on the opposite end portion of said strap for insertion in a receiving slot in a container, said tongue extending substantially longitudinally of said strap and comprising a length of material displaced from said strap and having a free end directed towards said enlarged locking head, and said locking tongue being attached to said strap along a juncture line extending substantially transversely of said strap at a location between said free end of said tongue and the outer edge of said opposite end portion of said strap.
 2. A closure device as defined in claim 1 wherein: said locking tongue is attached to said strap at said juncture line by an interconnecting shoulder portion angularly disposed with respect to said strap, said shoulder portion serving to hold said tongue at a permanently offset position from said strap at a spaced apart location with respect thereto.
 3. A closure device as defined in claim 2, and further including: a raised rib extending lengthwise on said tongue and having a base end securely joined to said opposite end portion of said strap, said rib serving to strengthen said tongue and to assist in holding said tongue in said offset position.
 4. A closure device as defined in claim 1, and further including: at least one elongated, raised rib on said strap extending lengthwise on said opposite end portion thereof both forwardly and rearwardly of said juncture line and thereby serving to prevent flexing of said strap along said juncture line and the resultant displacement of said tongue when it is engaged in a slot in a container.
 5. A closure device as defined in claim 1, and further including: a pair of elongated, raised ribs on said strap extending lengthwise on said opposite end portion of said strap both forwardly and rearwardly of said juncture line at laterally spaced locations on opposite sides of said juncture line.
 6. A closure device as defined in claim 1 wherein: a raised detent is formed on said free end of said tongue on the side thereof facing towards said elongated strap.
 7. A closure device as defined in claim 1 wherein: said enlarged locking head extends transversely of said strap on both sides thereof and defines therewith a substantially T-shaped end on said strap.
 8. On a fiberboard box having a pair of opposed closure flaps hingedly attached to parallel edges of the box and foldable inwardly towards each other to a box closing position, improved closure means releasably holding said closure flaps in said box closing position comprising: there being a first slot in one of said closure flaps adjacent one end thereof and in proximity to the inner, free edge thereof; there being a second slot in one wall of said box adjacent one edge thereof which is one of the edges cooperating to define an open end of said box closed by said closure flaps, and said one wall of said box extending at substantially right angles to the plane in which said flaps are disposed in said box closing position; and a flexible, elongated closure strap having an enlarged locking head at one end thereof restrainably engaged within said first slot and extending therefrom over said one edge of said box wall in overlying relation to said wall, said strap having a locking tongue adjacent the opposite end portion thereof which is restrainably engaged in said second slot, said tongue comprising a length of material integral with said strap and attached thereto along a juncture line extending transversely of said strap, and said tongue extending from said juncture line towards said enlarged locking head and terminating at a free end inserted within said second slot.
 9. A fiberboard box and closure means as defined in claim 8 wherein: there being a third slot is located at the other one of said closure flaps adjacent the same end thereof as said first slot and in proximity to the inner free edge thereof, said third slot being closer to said one wall of said box than said first slot, and said inner edges of said closure flaps being disposed in overlapping relation to each other when said flaps are folded to said box closing position, whereby one or the other of said closure flaps may be folded on top of the other and said third slot selectively utilized to receive said enlarged locking head of said closure strap to permit a looser fit of said closure strap on said box, and thereby to accommodate the expansion of the walls of said box when it is in a fully loaded condition.
 10. A fiberboard box and closure means as defined in claim 8 wherein: said second slot in said wall of said box is formed by striking a tab from said box wall and folding said tab inwardly along a hinge line where said tab joins said wall, said tab being folded inwardly to a position wherein it is in overlying relation to the inner surface of said box wall; and a raised detent on said free end of said locking tongue on the side thereof facing towards said elongated strap, said detent being restrainably engaged with the inner edge of said tab when said locking tongue is engaged within said second slot.
 11. A fiberboard box and closure means as defined in claim 8 wherein: said locking tongue is attached to said strap at said juncture line by an interconnecting shoulder portion angularly disposed with respect to said strap, said shoulder serving to hold said tongue at a permanently offset position from said strap at a spaced apart location with respect thereto.
 12. A fiberboard box and closure means as defined in claim 8, and further including: at least one elongated, raised rib on said strap extending lengthwise on said opposite end portion thereof both forwardly and rearwardly of said juncture line and thereby serving to prevent flexing of said strap along said juncture line and the resultant displacement of said tongue from engagement with said second slot in said box wall.
 13. A fiberboard box and closure means as defined in claim 8 wherein: said enlarged locking head on said closure strap is of greater width than said strap and extends transversely thereof, whereby said locking head defines with said strap a substantially T-shaped end on said strap, said T-shaped end being oriented transversely of said first slOt.
 14. A closure device for holding a hinged flap of a container in a closed position comprising: a flexible, elongated strap having an enlarged locking head at one end thereof for insertion through a receiving aperture in a container closure flap; and a locking tongue adjacent the opposite end portion of said strap for insertion in a receiving slot in a container, said tongue comprising a length of material displaced from said strap and attached thereto along a juncture line extending transversely of said strap, said tongue extending longitudinally of said strap from said juncture line towards said enlarged locking head and terminating at a free end, and said tongue being attached to said strap at said juncture line by an interconnecting shoulder portion angularly disposed with respect to said strap, said shoulder serving to hold said tongue at a permanently offset position from said strap at a spaced apart location with respect thereto. 